1. Field of the Invention
The present invention relates to a television tuner and a housing structure for an electronic equipment, and more particularly, to a television tuner, which receives therein a television tuner circuit and electronic parts that radiate electromagnetic wave noise, and a housing structure for an electronic equipment.
2. Description of the Related Art
Conventionally, an electronic equipment is known, in which electronic parts that radiate electromagnetic wave noise are received. In order to prevent leakage of electromagnetic wave noise, a housing for such electronic equipment is formed from a conductive material and configured to cover electronic parts. Also, a television tuner is conventionally known, in which a television tuner circuit that radiate electromagnetic wave noise is received.
FIG. 11 is a perspective view showing a conventional television tuner. FIG. 12 is a side view showing the conventional television tuner shown in FIG. 11. FIG. 13 is a partial cross sectional view showing the conventional television tuner shown in FIG. 12. A construction of a conventional television tuner 100 will be described with reference to FIGS. 11 to 13.
The conventional television tuner 100 comprises, as shown in FIGS. 11 to 13, a metallic bottom chassis 110, in which an electronic equipment is received, a front panel 120 made of a resin and mounted to a front side of the bottom chassis 110, a metallic top cover 130 mounted to an upper side of the bottom chassis 110, and a metallic grounding spring 140. As shown in FIGS. 12 and 13, the bottom chassis 110 comprises legs 111 and a support surface 112. Also, the top cover 130 comprises screwing portions 131.
The conventional television tuner 100 is placed on a placing surface through the legs 111 provided on the bottom chassis 110 in such a manner that the front panel 120 faces a front side. In this case, any portions as screwed are not present on the front side in order to make an outward appearance favorable. Also, the bottom chassis 110 and the top cover 130 on the conventional television tuner 100 are screwed to each other through the screwing portions 131, which are provided on sides and a rear surface side of the top cover 130, by means of conductive screws. Thus, since the bottom chassis 110 and the top cover 130 on the conventional television tuner 100 are screwed to each other by means of conductive screws, electric points of contact are present on the sides and the rear surface side. Thereby, a shielding effect is produced on the sides and the rear surface side of the television tuner 100.
Meanwhile, since screwing is not conventionally effected on a front side of the television tuner 100, there is a need for a construction that provides electric points of contact other than screwing. Concretely, by mounting the metallic grounding spring 140 in the form of a leaf spring between the support surface 112 provided on an upper portion of a front side of the bottom chassis 110 and the top cover 130, the bottom chassis 110 and the top cover 130 are brought into electric contact with each other. Thereby, a shielding effect can be produced on the front side of the television tuner 100. In this manner, with the conventional television tuner 100, conductive screws produce a shielding effect on the sides and the rear surface side and the grounding spring 140 produces a shielding effect on the front side.
However, the television tuner 100, shown in FIG. 13, uses the grounding spring 140 in order to produce the shielding effect, so that there is a problem that the number of parts is increased correspondingly.
Hereupon, in order to solve the above problems, it is conceivable to use other housing structures for an electronic equipment, in which a shielding effect is produced without the use of screws and the grounding spring 140 on the front side of the conventional television tuner 100 (see, for example, JP-A-6-291483 and JP-UM-A-58-155872).
JP-A-6-291483 described above discloses a housing structure for an electronic equipment, provided with an elastic comb-shaped portion that is formed on a peripheral edge of at least one of a conductive chassis receiving therein an electronic circuit and a conductive cover covering the chassis to prevent leakage of electromagnetic wave noise. With the construction disclosed in JP-A-6-291483, a shielding effect is produced by bringing the comb-shaped portion into press contact with the other.
Also, JP-UM-A-58-155872 described above discloses a casing construction for high frequency radio equipment, in which grooves are provided in the vicinity of and along end edges of both sides of a casing chassis and fitting projections are provided on a lid to correspond to the grooves. With the construction disclosed in JP-UM-A-58-155872, a shielding effect can be produced in those portions, in which the projections on the lid and the grooves of the casing chassis fit.